This invention relates generally to a device and method of separating particles contained in a liquid medium and, more particularly, to a device and method of removing sludge from molten salt bath. In even more particular aspects, the invention relates to a device that can periodically be inserted into a liquid medium that contains particulate material, and a method of using the device to capture and remove the particulate material therefrom.
Although the invention has application generally where particles in a liquid need to be separated, it is specifically designed for separating particles contained in molten salt baths as sludge which results from the surface treatment of various parts. The invention, although not specifically limited thereto, is particularly useful in removing sludge from a liquid salt bath, especially from an alkali molten salt bath used to quench parts that have been nitrided in a liquid salt nitriding bath. In this process, the parts to be nitrided are immersed for a time in a liquid salt nitriding bath at nitriding temperatures and they are then quenched in a liquid alkali metal carbonate bath. In one aspect of using the quenching bath, the nitrided and quenched parts are polished and then quenched again in the liquid alkali molten salt bath. In both of these instances, a certain amount of particulate matter in the form of xe2x80x9csludgexe2x80x9d builds up, which results from surface oxides and other surface contaminants which are removed from the surface of the parts being quenched. As the sludge builds up, the efficiency of the bath degrades, eventually to the point where the bath is no longer commercially viable. At this point in time, either the sludge has to be removed, or the entire bath bailed out and reconstituted. Prior art techniques of sludge removal have not been completely successful in some instances, and bailing out the bath and starting over can be very expensive.
Therefore, it is desired to have an effective way to remove particles from a liquid bath, especially sludge from a molten salt bath.
A method and device for removing particulate matter from a liquid medium, especially a molten salt bath, are provided. The structure includes a device for capturing and removing particulate matter from a liquid medium. The device includes a hollow tubular member having a first end and a second end, with an agitator disposed in the hollow tubular member and configured to generate circulation of the liquid with the particulate matter disposed therein. Fluid return openings are provided in the hollow tubular member to allow fluid to enter into the tubular member. A particulate capturing member is slidably mounted on the hollow tubular member and movable from a particulate retaining position to particulate discharging position. The device also includes a mechanism for engaging and moving said device into and out of the liquid.
In operation, the device is inserted into the liquid having the particulate matter, with the particulate matter collector in the particle collecting position. The agitator circulates the liquid having the particulate matter therein. A portion of the particulate matter is collected in the particulate matter collector during the circulation. Thereafter, the circulation is ceased and the device is removed from the liquid with the particulate matter in the particulate matter collector. The device is moved to a discharge position, and the particulate matter collector is moved to the particle discharge position to discharge the particulate matter.